fuel cell-performance and durability--electrocatalysts and ...fuel cell – performance and...
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2016 DOE Fuel Cell Technologies Office Annual Merit Review
2016 DOE Hydrogen and Fuel Cells Program Review
XYZ: Thrust Area # Co-ordinatorRod & Adam: FC PAD Directors
Wednesday, June 8th, 2016
FC-PADFuel Cell – Performance and DurabilityFC136 – Electrocatalysts and Supports
This presentation does not contain any proprietary, confidential, or otherwise restricted information.
2016 DOE Fuel Cell Technologies Office Annual Merit Review
June 8, 2016Thrust Coordinator: Debbie Myers
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2016 DOE Fuel Cell Technologies Office Annual Merit Review
Component Thrust 1: Electrocatalysts and Supports
Overview: Three component thrusts
focusing on catalyst, electrode and ionomer/GDL/plates
Three crosscutting thrusts focusing on modeling, evaluation, and characterization
Thrust Area 1, Electrocatalysts and Supports, is the focus of this presentation
Thrust Area 1 is synergistic with Thrust Areas 2, 3, and 5 and supported by Thrust Areas 4 and 6
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2016 DOE Fuel Cell Technologies Office Annual Merit Review
Debbie Myers Nancy KariukiXiaoping WangDennis PapadiasRajesh Ahluwalia
Rangachary MukundanRod BorupYu Seung Kim
Karren MoreDavid Cullen
Shyam Kocha KC Neyerlin Jason Christ Jason Zack
IRD (Catalysts, MEAs) Umicore (Catalysts) Johnson Matthey (Catalysts, CCMs; as part of FC106) Ion Power (CCMs) Korea Institute of Energy Research (micro-electrode
cell studies)
FC-PAD contributors to this presentation
Current Collaborators
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2016 DOE Fuel Cell Technologies Office Annual Merit Review
FC-PAD Thrust 1: Overview
• Project start date: 10/01/2015• Project end date: 09/30/2020
• The electrocatalyst remains a challenge for reducing the cost to meet system cost targets
• Durability targets have not been met• The catalyst, its interaction with other
electrode components, the stability of alloying components, and the effect of this instability are not fully understood and are key to achieving performance, cost, and durability targets.
Timeline Barriers
• IRD, New Mexico• Umicore, Germany• NECC, Japan• GM, USA• Ion Power, USA• Tanaka Kikinzoku Kogyo (TKK), Japan• Johnson Matthey, United Kingdom• Korea Institute of Energy Research (KIER)• Partners to be added by DOE DE-FOA-
0001412
National Labs
Partners/Collaborators To Date• ANL, LANL, NREL, and ORNL
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2016 DOE Fuel Cell Technologies Office Annual Merit Review
Relevance and Approach Thrust Area Objectives
— Realize the ORR mass activity benefits of advanced Pt-based cathode electrocatalysts in high current density, air performance for over 5,000 operating hours and with low PGM loading (<0.1 mg-Pt/cm2)
Catalyst and catalyst support durability and degradation mechanisms— Elucidate catalyst and support degradation mechanisms as a function of catalyst and support
physicochemical properties and cell operating conditions— Quantify catalyst and support stability during accelerated stress tests and start-up and shut-down
transients using in-cell measurements— Determine stability of catalyst components, catalyst and support composition and structural changes
Catalyst/support interactions— Understand interplay between the catalyst and support properties and their mutual interactions— Determine the effects of carbon type (e.g., high, medium, and low surface area) and carbon dopants on
the strength of the catalyst/support and ionomer/support interactions— Investigate the impact of these interactions on catalyst and support stability, durability, and
performance
Ex-situ analysis of catalyst instability on cathode-catalyst-layer properties— Quantify the impact of catalyst degradation on the properties defining the performance of the cathode
catalyst layer (e.g., impact of base metal leaching from Pt alloy catalyst on proton conductivity, oxygen permeability, and water uptake in ionomer)
Approach - Achieve Objectives by studying:
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2016 DOE Fuel Cell Technologies Office Annual Merit Review
Electrocatalysts currently under study in FC-PAD
Electrocatalysts being studied for foundational understanding of advanced catalysts
Commercial Sources IRD:
‒ IRD CAT0023, 55wt% PtCo/C, 6.0 nm TEM Umicore:
‒ Elyst Pt50 0550; 45.9wt% Pt, 5.5 nm XRD‒ Elyst P30 0670; 27.5 wt% Pt; 3 wt% Co, 4.4 nm TEM
NEChemcat:‒ PtCo/NE-GM‒ Core-shell Pt ML/Pd/NE-H
TKK: ‒ TEC10E50E, Pt/HSC, 47.5wt% Pt, 2.5 nm XRD‒ TEC36E52, Pt3Co/HSC, 46.5 wt% Pt, 4.7 wt% Co, 5.7 nm TEM
Johnson Matthey:‒ Pt3Co/HSC, 40 wt% Pt, 4.9, 8.7, 14.3 nm TEM ‒ Dealloyed-Pt1.3Ni/HSC, 29.1 wt% Pt, 6.68 wt% Ni, 5.1 nm TEM
National Lab Sources
NREL ETFECS ANL Frame
Automotive Source General Motors
– Proprietary
Academic Source USC Pt/ACCC
✓
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2016 DOE Fuel Cell Technologies Office Annual Merit Review
Platinum Alloy Electrocatalysts in FC-PAD
Umicore Pt7Co3/C Mean particle size of 4.4 nm
IRD PtCo/C Mean particle size of 6.0 nm
“Spongy” PtCo
morphology
Three JM Pt3Co/C Mean particle sizes of
4.9, 8.7, 14.3 nm
UT AustinUT Austin
TKK Pt3Co/C Mean particle size of 5.7 nm
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2016 DOE Fuel Cell Technologies Office Annual Merit Review
Accomplishment: Ex situ measurement of ORR Activity Baseline oxygen reduction reaction
(ORR) activity of catalysts determined using thin-film rotating disk electrode (RDE) method developed and described in FC111 (with ionomer in thin film)
Electrochemically-active surface area of “baseline” high surface area Pt (TKK TEC10E50) is twice that of platinum alloy catalysts due to alloying heat treatment step leading to particle growth
Ionomer in electrode suppresses ORR activity, by 40% for Umicore Pt3Co
IRD PtCo catalyst showed lower ORR activity in RDE than in MEA (cf. FC137)
Platinum alloys under consideration meet or exceed DOE 2020 ORR activity target (>440 mA/mg-Pt)
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2016 DOE Fuel Cell Technologies Office Annual Merit Review
Solid Squares: TKK 5.7 nm Pt3Co potentiostaticSolid diamonds: TKK 5.7 nm Pt3Co potential cyclingOpen Diamonds: IRD 7.2 nm Pt3Co Cycling
Potentiostatic Pt dissolution increases withdecreasing particle size for the JM Pt3Co catalysts
Potentiostatic Co dissolution is highest for the JMPt3Co/C catalyst with the largest particle size
TKK 5.7 nm Pt3Co catalyst shows a higher extent ofPt dissolution than all of the JM catalysts, eventhose with much larger particle size
Pt dissolution is higher for JM 4.9 nm Pt3Co ascompared to that of a Pt catalyst with very similarPSD (5.0 nm Pt)
Steady-state Co dissolution increases withincreasing potential above 1.1 V, consistent withpotentiostatic and potential cycling dissolution ratedata
Potential cycling Pt dissolution rate lower for IRD“spongy” Pt3Co compared to TKK “solid” Pt3Co,whereas Co dissolution rate is much higher
Dissolution data illustrate detrimental impact of cell voltages >1.0 V on base metal retention in nanoparticles
Accomplishment: Potential Dependence of Pt and Co dissolution
ICP-MS detection of dissolved metals in 0.57 M HClO4
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2016 DOE Fuel Cell Technologies Office Annual Merit Review
0.0
0.5
1.0
1.5
2.0
2.5
0.8 0.9 1 1.1 1.2 1.3
Exte
nt o
f oxi
datio
n at
8 h
(O
/ Sur
face
Pt)
Potential Hold Value (V vs RHE)
Pt3Co 4.9 nm
Pt 5.0 nm
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
1.2
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Pote
ntia
l (V
vs. R
HE)
Chan
ge in
WL
for s
urfa
ce P
t
XAFS Scan No.
Pt d-PtNiPt3Co 10-35 Potential
Extent of Oxidation determined via voltammetric charge for oxide reduction after 8 hour potential holds in dilute aqueous HClO4 electrolyte
Extent of oxidation determined via height of Pt L3 X-ray absorption “white line” after 30 min potential holds in dilute aqueous HClO4 electrolyte
Accomplishment: Potential Dependence of Alloy Catalyst Oxidation
, 5.0 nm, 4.9 nm
, 5.1 nm Pt alloy particles show greater extent of oxidation of surface Pt than Pt particles having approximately the same size distribution.
These data, and cyclic voltammetry data, are used as input to the dissolution model to find the links between oxide formation and dissolution under potentiostatic and potential cycling conditions.
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2016 DOE Fuel Cell Technologies Office Annual Merit Review
Accomplishment: Thermodynamics of PtOx Formation Pt3Co Alloy
XPS Study and DFT/Monte Carlo Simulations* Potentials < 0.65 V, H2O(ad) is the dominant species Above 0.65 V, OH(ad) forms from oxidation of H2O(ad)
Above 0.8 V, OH(ad) further oxidizes to O(ad)
H.S. Casalongue, et al., “Direct observation of the oxygenated species during oxygen reduction reaction on a platinum fuel cell cathode”, Nature Communications, Dec, 2013.
All data from aqueous tests with 0.57 M HClO4
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2016 DOE Fuel Cell Technologies Office Annual Merit Review
Accomplishment: Kinetics of PtOx Formation for Pt3Co Alloy
Developed a procedure for determining the rate constants for kinetics of PtOx formation by using the CV oxidation and reduction scans (8 h hold at high potential, 10 mV/s scan rate) Only 10-30 s needed to form or reduce the oxides during
the potential scans
-1.6
-1.4
-1.2
-1.0
-0.8
-0.6
-0.4
-0.2
0.0
0.2
0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2
Cur
rent
, mA.
cm-2
Potential, V
0.80 V0.90 V0.95 V1.00 V1.05 V1.15 V1.20 V
-0.6
-0.5
-0.4
-0.3
-0.2
-0.1
0.0
0.1
0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1
Cur
rent
, mA.
cm-2
Potential, V
1.05 V
PtO
PtO2
PtOH
-0.7
-0.6
-0.5
-0.4
-0.3
-0.2
-0.1
0.0
0.1
0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2
Cur
rent
, mA.
cm-2
Potential, V
1.2 V
PtO
PtO2PtOH
Oxidation Potential (E0)
Symmetry Factor (α)
Pt + H2O = PtOH + H+ + e- 0.740 V 0.735
PtOH = PtO + H+ + e- 1.220 V 0.6
PtO + H2O = PtO2 + 2H+ + 2e- 1.045 V 0.55
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2016 DOE Fuel Cell Technologies Office Annual Merit Review
Accomplishment: Thermodynamics of Pt dissolution from Pt3Co Alloy
Standard potential (E0) for Pt dissolution (Pt = Pt2+ + 2e-) from Pt3Co alloy and its dependence on particle diameter Pt3Co has higher E0 than Pt and is
more stable at low potentials
Pt = Pt2+ + 2e-
PtOH + H+ = Pt2+ + H2O + e-
PtO + 2H+ = Pt2+ + H2O PtO2 + 4H+ + 2e- = Pt2+ + 2H2O
Pt3Co has higher dissolution potential,but is less stable than Pt at high potentials
Thermodynamics of electrochemical and chemical dissolution of Pt
Derived from dissolution data at 0.85 V
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2016 DOE Fuel Cell Technologies Office Annual Merit Review
Accomplishment: Kinetics of Pt dissolution from Pt3Co AlloyRate constants derived from potentiostatic dissolution predict the behavior observed in cyclic tests: triangle wave, 10 mV/s scan rate, fixed lower potential limit (0.4 V), variable upper potential limit
Cyclic Potential DissolutionUpper Potential Limit Above 1.1 V Pt dissolves as PtOH Pt2+ re-deposits as Pt during
cathodic scanUpper Potential Limit Below 1.1 V Pt dissolves as Pt and PtOH No significant re-deposition
during cathodic scan
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2016 DOE Fuel Cell Technologies Office Annual Merit Review
Accomplishment: Thermodynamics of Co Dissolution from Pt3Co Alloy
Surface Co is thermodynamically unstable (E0=0.280 V) and dissolves during pre-treatment to create a core-shell structure. The thickness of Pt skin is proportional to particle size.
At higher potentials, SS-Co may be stabilized by the formation of sub-surface oxides of Co. Oxygen can coordinate with SS-
Co: ∆G = -166 kJ/mol for PtO +Co = Pt + CoO
XANES measurements of∆µ for dealloyed PtM3
Sub-surface Co (SS-Co) has a dissolution potential (E0) of 1.158 V, and it increases as Pt skin gets thicker.
0.8 0.9 1 1.1 1.2 1.3-0.5
-0.4
-0.3
-0.2
-0.1
0
0.1
Hold potential, V
RT/n
Fln
(aCo
), V
d=4.9 nm
d=8.1 nm
d=14.8 nm
KM Caldwell, et al., “Spectroscopic in situ measurements of the relative Pt skin thicknesses and porosities of dealloyed PtMn (Ni, CO) electrocatalysts”, Phys. Chem. C, 757-765, 2015.
0.8 0.85 0.9 0.95 1 1.05 1.11.14
1.15
1.16
1.17
1.18
1.19
1.2
Depth of de-alloying (atomic layers)
E 0(C
o), V
Pt/C
o at
omic
ratio
0
1
2
3
4
5
GDE as-received
GDEConditioned
GDE 0.85 V,72 h
4.9 nm 8.1 nm 14.8 nm
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2016 DOE Fuel Cell Technologies Office Annual Merit Review
Accomplishment: Kinetics of Co Dissolution from Pt3Co AlloyThe rate constant for SS-Co dissolution depends on potential/surface oxides Need fundamental understanding of oxygen coordination
with Co in core-shell Pt3CoUnder potential cycling, the kinetics of change in SS-Co activity are slow The derived activity on a repeat cycle is far from equilibrium
and shows hysteresis 10-50 times higher Co dissolution after 500 triangle cycles
(17-25 h) than potentiostatic hold for 72 h Difficult to correlate the changes in activities of SS-Co and Pt
oxides in Pt3Co
Potential, V
0.9 1 1.1 1.2 1.310 -15
10 -10
10 -5
10 0
Potentiostatic
Diss
olut
ion
Rate
Cons
tant
, mol
cm-3
s-1 α1=0.8
0.4 0.6 0.8 1 1.2 1.40
5
10
15
20
25
30
Potential, V
Up-scan
ln(a
Co)
Triangle cycle
Down-scan
0 100 200 300 400 5000
0.5
1
1.5
2
2.5
0.4-1.0V
Number of cycles
0.4-1.1V
0.4-1.2 V
0.4-1.3 V
Co C
once
ntra
tion,
μM
TKK CatalystCycling 10 mV/s
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2016 DOE Fuel Cell Technologies Office Annual Merit Review
Impact of Base Metal on Ionomer Oxygen Permeability
-80
-60
-40
-20
0
20
40
60
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4
Curr
ent [
nA]
Potential [V] vs RHE
BeforeNiClO4 drop
After NiClO4drop
H+ form
Ni2+ form
-300
-250
-200
-150
-100
-50
0
50
0 0.2 0.4 0.6 0.8 1 1.2 1.4
Curr
ent [
nA]
Potential [V] vs RHE
BeforeNiClO4 drop
After NiClO4drop
H+ form
Ni2+ form
RDE showed 6% decrease in oxygen permeability of 0.7 µm ionomer film for 10 mM Ni2+ in 0.1 M HClO4; 29% decrease in ORR kinetic current at 0.9 V. (FC106; 2015 AMR)
Solid state microelectrode cell showed ∼15% decrease in oxygen permeability with addition of Ni(ClO4)2 and decrease in ORR kinetics
Room temperature, 100% RH
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2016 DOE Fuel Cell Technologies Office Annual Merit Review
Carbon Corrosion Measurement Matrix for Mechanistic Definition
Vary Upper Potential Limit0.95 V – 0.40 V0.90 V – 0.40 V0.85 V – 0.40 V…..0.55 V – 0.40 V
Vary Lower Potential Limit0.95 V – 0.40 V0.95 V – 0.45 V0.95 V – 0.50 V…..0.95 V – 0.80 V
E (High Surface Area, Ketjen); TEC10E20E; 18.5 wt% Pt/C, 0.15 mg-Pt/cm² EA (Graphitized or Low Surface Area); TEC10EA40E, 38.7 wt% Pt/C, 0.25 mg-Pt/cm²V (Vulcan); TEC10V40E, 33.9 wt% Pt, 0.17 mg-Pt/cm²
Experimentally measure carbon corrosion during operation– Direct CO2 measurement by NDIR
Modeling to identify carbon corrosion mechanism and rates related to carbon and Pt surface oxidation
Carbon thermodynamics
Adapted from M. Pourbaix, Atlas of Electrochemical Equilibria (1966)
Three Types of Carbon Supports
Potential Reset Times0.5 min1 min2 min5 min
Fuel Cell operation largely as per DOE/FCTT Drive Cycle Protocol
Ion Power MEAs with SGL 25BC GDLs in 50-cm2 quad-serpentine flow field from Fuel Cell Technologies, 80oC cell temp.; H2: 670 sccm, 83oC dew point, 3.4 psig; Air: 1800 sccm, 83oC dew point
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2016 DOE Fuel Cell Technologies Office Annual Merit Review
Measured Carbon Corrosion During Drive-Cycle
500 530 560 590 620 650 680
CO2
Sign
al (N
DIR)
/ pp
m C
O2
Time / sec
DL061114 WetDrive Cycling
Non-zero CO2 evolution with all carbon types during drive cycle As power decreases, voltage increases During voltage rises, CO2 evolves from the catalyst After spike, CO2 evolution is reduced
– surface passivation Higher ‘steady-state’ CO2 production at 1.2 A/cm2
– reducing surface/forming adsorbed species
0
5
10
15
20
25
30
0 0.2 0.4 0.6 0.8 1 1.2
Corr
osio
n ra
te (μ
g Ccm
-2h-1
)
Cell potential (V)
Vulcan XC-72
Transition from:1.2 to 0.02 A/cm2
0.02 A/cm2
1.2 A/cm2
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2016 DOE Fuel Cell Technologies Office Annual Merit Review
Accomplishment: Comparison of corrosion of three carbon types
For potential cycles to 0.8 V and higher (fixed 0.4 V low potential), corrosion rates are lower for graphitized carbon (EA-type) than for other carbons (E-type, V-type)
For potential cycles below 0.8 V, the magnitude of corrosion upon a step change in potential is similar for all carbons
Extents of corrosion linked to formation of carbon oxides and interaction of these oxides with Pt hydroxide and oxide and water
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1) Formation of active (C#OH) and passive (C#Ox)carbon surface oxide species
2) Formation of OH and oxide surface species on Pt
3) Oxidation of active carbon surface species (C#OH) with OH spill-over from Pt at intermediate potentials
4) Oxidation of active carbon surface species (C#OH) with H2O at high potentials
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2016 DOE Fuel Cell Technologies Office Annual Merit Review
Accomplishment: Transient Corrosion Mechanism
Low corrosion rate if cell held at high cell potential- Defect sites passivated by C#Ox
- Pt exists mainly as PtO at 0.95 V and as Pt at 0.6 V Small corrosion spike in transitioning from HCP to LCP
- C#Ox begins to convert to active C#OH - PtO converts to PtOH- Spikes due to reaction between C#OH and PtOH- Increasing lower cell potential from 0.4 to 0.55 V decreases corrosion during
transition due to lower equilibrium C#OH coverage Corrosion rate slowly decreases as the cell is held at low cell potential
- PtOH converts to Pt Large corrosion spike in transitioning from LCP to HCP
- Spikes due to rapid reaction between C#OH and H2O at elevated potential- C#OH converts to C#Ox over longer time- PtOH converts to PtO over longer time
Varied Upper Potential Limit0.95 V – 0.40 V0.90 V – 0.40 V0.85 V – 0.40 V…..0.55 V – 0.40 V
Varied Lower Potential Limit0.95 V – 0.40 V0.95 V – 0.45 V0.95 V – 0.50 V…..0.95 V – 0.80 V
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2016 DOE Fuel Cell Technologies Office Annual Merit Review
Accomplishment: Steady-State Corrosion Model
Steady-state corrosion rates determined from NDIR data for CO2 emission after 5-min hold at potential
Over 0.4-0.95 V cathode potentials, steady-state corrosion rate peaks at ~0.6 V
Peak corrosion rates are similar for E-Type, V-Type and EA-Type carbons
Steady-state corrosion rate slows above 0.6 V due to formation of passive oxides
Pt converts to PtOH above 0.6 V PtOH converts to PtO above 0.9 V Since PtOH only forms above 0.6 V,
the observed corrosion peaks are due to C#OH reacting with H2O.
[3] Casalongue, H.S., et al. (2013). Nature Communications, 4, 2817.
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2016 DOE Fuel Cell Technologies Office Annual Merit Review
Summary of Mechanism of Carbon Corrosion during Drive Cycles
Formation of surface oxides on carbon defect sites (C#)- Defect sites hydrolyze to form active oxides (C#OH) at cathode potential (E) >0.3 V- C#OH converts to passive oxides (C#Ox) at E >0.8 V
Carbon corrosion is catalyzed by PtOH- PtOH begins to form at E >0.6 V- PtOH converts to PtO at E >0.9 V
Steady-state corrosion mechanism- Corrosion rate peaks at ~0.6 V cathode potential, small at 0.95 V- Corrosion is primarily due to oxidation of C#OH by H2O - All three carbons (Ketjenblack, Vulcan and graphitized Ketjenblack) show similar
corrosion rates
Carbon corrosion under transient potentials can be much higher - Spikes in corrosion rates while transitioning from high (0.95 V) to low cell potentials
(0.4 V) are due to formation of C#OH and its and its reaction with PtOH- Larger spikes in corrosion rates while transitioning from low (0.4 V) to high cell
potentials (0.95 V) are due to accelerated oxidation of C#OH by H2O at elevated potentials
Transient corrosion rates: E-Type ~ V-Type >> EA-Type
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2016 DOE Fuel Cell Technologies Office Annual Merit Review
Proposed Near-term Future Work
Potentiostatic and potential cycling dissolution and oxide coverage measurements for IRD Pt3Co and Umicore Pt3Co‒ Comparison of catalysts with “spongy” morphology to “solid” morphology
Measurements of Pt re-deposition rates as a function of potential Application of catalyst corrosion model to cell data using TEM-EDAX and XRF
quantification of Pt and Co in cell components EXAFS analysis of changes in Pt and Co coordination numbers and bond distances
for catalysts from cycled MEAs Delta-µ XANES analysis of Pt3Co oxide structure as a function of potential (in
collaboration with General Motors) Solid state microelectrode measurements of oxygen permeability
‒ Impact of Co2+ and Ni2+ as a function of relative humidity and temperature
Carbon corrosion studies for Pt alloys vs. Pt of similar particle size distribution Pt dissolution as a function of carbon type and correlation with changes in particle
size distribution and electrochemically-active surface area
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2016 DOE Fuel Cell Technologies Office Annual Merit Review
Summary Relevance: Realize the ORR mass activity benefits of advanced Pt-based cathode
electrocatalysts in high current density, air performance for over 5,000 operating hours and with low PGM loading (<0.1 mg-Pt/cm2)
Approach: Studies of catalyst and catalyst support durability and degradation mechanisms, catalyst/support interactions, and effects of catalyst instability on cathode-catalyst-layer properties
Accomplishments and Progress: Determined potential and potential cycling dependence of Pt and Co dissolution from several Pt3Co alloys, oxide formation kinetics and thermodynamics, and developed a model based on these data for the thermodynamics and kinetics of Pt and Co loss from catalyst particles; Initiated solid-state cell work for oxygen permeability measurements in ionomer thin films; Developed a model for carbon corrosion during drive cycle.
Future work: Potentiostatic and potential cycling dissolution and oxide coverage measurements for IRD Pt3Co and Umicore Pt3Co and other advanced catalysts with alternative morphologies/properties; Measure Pt re-deposition rates; Apply catalyst corrosion model to MEA data; Determine changes in catalyst atomic composition and distribution using XANES; Solid-state measurements of effect of base metal on oxygen permeability; Refinement of cathode performance and durability model using ex situ-measured component properties.